Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

I recently replaced an ~8 year old Heatilator Direct Vent Gas Fireplace with a new Lennox Fireplace. Both are Multi-sided, and 38,000 Btu. The Heatilator used 5"x8" DV venting, and of course the Lennox requires 4"x7" Secure Vent.

Is there an adapter availiable that I can utilize to go from the 4"x7" from the appliance, to the existing 5"x7" venting? Also, other than the fact that Lennox chooses to use the Secure Vent, is there any specifications related to exhaust vs intake that I need to be aware of?

Who makes the "Secure Vent"?
If its not simpson duravent then I doubt there is an adaptor. The old DV (D series) vent is made by simpson duravent and has a twist lock system on it. Usually the only time adaptors are made is if one vendor switches from one venting to another.

ditto Collin

The vent pipe is part of a listed system and can NOT be mixed and matched.

FYI, Heatilator no longer makes their VP pipe series.

Just curious, why did you replace the HL?

You really should have investigated these issues before you purchased the new Fp. Yes, the venting configurations allowed are only those shown in the listed instructions that came with your fireplace. If you can afford a multi-sided Fp, you certainly should be able to afford the vent pipe. Didn't you discuss this with your hearth retailer?

The fact that you recognize Lennox "requires 4"x7" Secure Vent" and "other than the fact that Lennox chooses to use the Secure Vent" tells me you already knew you should be using only the pipe listed for this Fp. This sounds fishy to me.

Yes, I already knew of the different vent piping. I was just curious as to the reasons (engineering) behind it. You say it is because it is part of a "listed" system, and cannot be mixed or matched, which is all I have been able to get from the hearth dealer. When I ask how this is determined, all I can get from anyone is basically, because that's the way it is. I have no problem changing the venting out, and will do so. I just thought that there may be someone out there who knows why this is.

The fireplace is tested as a "system" with the venting by UL or some other testing agency. That is the only venting it is approved to be used with. Any other not approved venting is not tested with this system and since you are putting a box of fire in your house you could potentially burn it down.

Originally posted by jtp10181 The fireplace is tested as a "system" with the venting by UL or some other testing agency. That is the only venting it is approved to be used with. Any other not approved venting is not tested with this system and since you are putting a box of fire in your house you could potentially burn it down.

I think it IS possible.

I always smile when people say you can't or shouldn't do something but can't give you a good reason why not. I am replacing a heatilator fireplace that uses 5 x 8 venting with another fireplace that uses 4 x 6 5/8 venting. Since the 4 x 6 5/8 venting is much cheaper than the heatilator 5 x 8 venting I will probably just put in all new venting; however, duravent DOES make an adapter that goes from 4 x 6 5/8 to 5 x 8, although they do say of course to check with the fireplace vendor to see if that's OK to do. I can't imagine why there would be a problem going from a smaller vent pipe to a larger one, after all, the smaller vent pipe ultimately vents to the great outdoors which is much larger than 5 x 8. I could see an issue trying to go from a fire place with a 5 x 8 vent to a smaller sized vent.

Another road test candidate for air bags....

So you're saying that in your vast experience working in a fireplace mfrs's R&D test lab, you don't foresee a problem?

It is an unknown quantity unless tested and listed. Therefore, it would be in violation of every major model building code, fire code and nationally recognized standard. It you suffered a loss after being warned here, your insurnace company may be able to deny your claim based upon gross negligence on your part. Should somebody else get hurt, you may not only be personally liable but criminal charges possibly could apply. Regardless, if not tested and listed, then the warranty and listing of the appliance is null and void. If you went to sell the house and failed to disclose this defect, you could be in big trouble should someone down the road get hurt or suffer damages.

Why is it everyone thinks they are an expert in fireplaces? Gee, let's see, if I can somehow adapt pipe A to pipe B then how could be be a problem? Just for starters, try fire, carbon monoxide poisoning, odors, soot damage delayed ignition, oxygen starvation, flame proving dropout, etc.

Scary

Boy, that does sound scary. I guess with all your years of experience in a mfging lab you could describe how going from a 4 x 6 5/8 direct vent to a 5 x 8 direct vent could result in any of these events occurring.
Like I said, you wouldn't want to go from 5 x 8 to 4 x 6 5/8. The things you mention would become issues in that scenario.

Draft is not the same in every appliance. Take boilers for example. Some boiler are vented with 5", some 6", etc.... It has very little to do with the boiler output and more to do with the flue gas paths and resistance to flow. the physics of "the chimney effect" change with each specific appliance. Your old Heatilator may have had a different coefficient of flow than the new Lennox. The fact at hand is that we don't know. The manufacturer's do. They test this equipment under specified conditions in order for it to be rated. No rating, No selling.

As stated the repercussions of installing an appliance against the manufacturer's specifications are not only ill-advised, but subject you to serious legal issues. The court precedents are long and distinguished. Should any of us, as licensed professionals, install an appliance against the manufacturer's spec, we could be subject to fines, losing our license, etc..

Like I said, you wouldn't want to go from 5 x 8 to 4 x 6 5/8. The things you mention would become issues in that scenario.

Actually HHT Makes a DVP-SLP24 which converts from the 8" DVP to the 6-5/8" SLP pipe. Of course it has been tested and approved specifically for certain fireplaces, with special venting considerations.

Going from 4" to five exhaust is going to create to much draw. Your flame will be ghosting ( lifting off the burner ) resulting in thermopile droping out. Everytime the wind blows your fireplace will be shutting down. If you can't get an approved adapter for that unit than change it out.